I have had numerous requests for a turn-key throttle solution for RC systems. So, to that end, I am starting this tutorial for the technically challenged who want the basics of how to build a throttle for an RC throttle interface system with off the shelf parts.

Bear in mind, I am not the first to setup a throttle like this, nor am I an electronics engineer. In fact, I am somewhat electronically challenged myself. However, I have been forced to learn some basics for the good of my hobby and the industry as a whole. I want to share a basic throttle layout here for beginners to refer to. This is obviously super simple for the very technically inclined members of our forum. But, it should help those who are not as technically savy.

You can use other brands of BEC and servo tester if you desire, especially if you want to save some money. But, these are the items readily available at my local hobby shop. So, that is why I chose them. They are also high quality and work well together.

NOTE: All individual instructions are written in the caption boxes below each picture for reference.

Attachments

Here are the components layed out as they come in the package.

step1.jpg (139.95 KiB) Viewed 11436 times

First, remove the board from the Servo Tester case.

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Next, carefully remove the Potentiometer from the circuit board. Save this part as well as the knob. They can be reused later for an add-on to the throttle if desired (more on that later).

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Next, flip the board over and locate the solder points from the pottentiometer you just removed.

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Next, solder the throttle wires to the potentiometer points on the rear of the board as shown. Be sure to use the color combination shown here (black, brown, blue).

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Now, take the BEC and locate the 3 wire lead coming from it, along with the two (black and red) wires at the rear of the Servo Tester board as shown.

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Now, using ONLY the red and black wires from the output of the BEC, solder them to the points on the Servo Tester board that originally held the original red and black wires (clip the left over wires that are dangling from the Servo Tester board). The orange (third) wire coming from the BEC is no longer used. I just clip it short.

Next, once all wiring is finished, I normally wrap the BEC in tape, then foil, then tape again. This is to reduce/eliminate RF interfereance from the switching circuit of the BEC. That RF can bother the servo tester and create some glitches.

The bottom picture shows two completed throttles next to each other. The lower throttle has both boards merely taped together (using tape to insulate the two from shorting against each other). Wide heat shrink tubing can be used as well for a more finished look, as well as better durability. The top throttle has both boards mounted in a simple Radio Shack project box.

The throttle is now finished, ready to use! You merely supply 24 to 48 volts to the black and red input wires (the two bare wires hanging out the side) and plug the other wire into your RC controller, and you are ready to go!

Attachments

Here the foil is wrapped around the BEC. It will be taped next.

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Here is a completed throttle. This is the smallest and simplest arrangement with the servo tester and BEC merely taped (or heat shrinked) together. IMPORTANT------ Be sure to wrap the BEC in tape after the foil wrap or the foil will short out the Servo Tester board if they touch!!!!!

finished1.jpg (137.88 KiB) Viewed 11416 times

1% of the world's population can think "Outside the box". The rest are firmly stuck within the box. Where are you?

Lastly, I figured a simple way of reusing the Pot that was removed from the Servo Tester board as a throttle end point limiter.

I do not have good pictures of the wiring to do this. But, basically, you run the blue wire (from the Magura throttle) to the second Pot (the one we removed earlier). This wire should go to the center terminal on that removed Pot. Next, you run a separate wire from the terminal to the right of that center pin on the Pot to the terminal on the back of the Servo Tester board that the blue wire should have gone. This, effectively, gives you an adjustable throttle end point.

Now, this end point adjustment is NOT a current limiter. It is a throttle end point adjustment. So, when that Pot is set at 50%, your twist grip throttle will only output 50% at full throttle rotation. This limits the top speed attained and increases throttle resolution making for much smoother throttle response. This is especially helpful for high speed/power setups where you want to be able to limit speed and soften throttle response for a beginner who wants to ride it.

Adjustable throttle is shown to the right of a non-adjustable throttle.

This particular throttle was built for my 12.5kw trike.

Attachments

two throttles.jpg (124.9 KiB) Viewed 11401 times

1% of the world's population can think "Outside the box". The rest are firmly stuck within the box. Where are you?

Thanks for posting that Matt...I'll be picking up a Magura and doing this as well.What's your opinion of the Magura?

Seems like Magura makes throttles for pull cable throttles too.

I bought a lousy thumb pot throttle that I'm not happy with at all.It has a weird full throttle catch which is not what you want in a throttle IMHO.I've gone through great lengths on cars to insure that the throttle neversticks wide open, and this company built a throttle thatdoes just that Its a low tech cruise control I guess...which may be good for a low power setup.

"If you don't follow your dreams, you might as well be a vegetable." Burt Munro

The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself.Therefore all progress depends on the unreasonable man. -- George Bernard Shaw

I have mixed emotions about this twist grip throttle. The quality is OK, I suppose. My beef is the fact that it is all plastic. However, the plastic is thick and well molded. Also the return spring is pretty stiff. Not horribly so, but a touch stiffer than I would normally choose. Other than that, it is really pretty decent. The price is good as well.

Oh, also, I plan to make a thumb attachment for this to make a basic thumb throttle. If you picture cutting this twist grip very short so only 1/2 inch of the twist barrel is left, then add a thumb tap to the remaining twis barrel portion. Pretty simple. It could be cut to half length too for a half throttle like a half grip, twist shifter.

Matt

1% of the world's population can think "Outside the box". The rest are firmly stuck within the box. Where are you?

Yes im afraid he passed away week ago ? Matt. Helen and Rhett had previously discussed quality of life issues in case a situation like this arose and both agreed to pull the plug if it was determinedquality of life would be comprimised, seeing Rhetts injuries were extensive AND to the frontal lobe of the brain the decisions was made by Helen to take Rhett off like support...very sad indeed he was such a nice blokeat least he lived a full and productive life, he flew all around the world as a pilot as well as well as being a tragic RC addict Might very well be the first rider to die on a lecky bike too

After we wire and solder it all up.....is there anything we need to do to the controller? Is there some type of calibration involved? If this sounds like a strange question allow me to clarify.

As I understand it, the FETs allow current to "pass" during the time they are on (duty cycle). If we are into low speed cruising from time to time and barely twist the throttle then the FETs will have a very short duty cycle BUT may still heat up when they are inbetween pulses. Is this correct? If so do we need to ensure a minimum duty cycle - minimum command voltage (oh, like 50% of battery V) or is this a non-issue?

If so do we need to ensure a minimum duty cycle - minimum command voltage (oh, like 50% of battery V) or is this a non-issue?

The throttle pulses aren't used to drive the output stage directly, there's a microcontroller in between in the ESC.

When you first power it up, the ESC looks for a baseline stream of pulses (1 millisecond width) which corresponds to zero throttle. If it sees these pulses, it then goes in to idle (motor stationary, ready to start).

Opening the throttle increases the pulse width proportionately, up to a max of 2 milliseconds, which is what this interface circuit does. The ESC takes care of the rest (i.e. spinning the motor).

If so do we need to ensure a minimum duty cycle - minimum command voltage (oh, like 50% of battery V) or is this a non-issue?

The throttle pulses aren't used to drive the output stage directly, there's a microcontroller in between in the ESC.

When you first power it up, the ESC looks for a baseline stream of pulses (1 millisecond width) which corresponds to zero throttle. If it sees these pulses, it then goes in to idle (motor stationary, ready to start).

Opening the throttle increases the pulse width proportionately, up to a max of 2 milliseconds, which is what this interface circuit does. The ESC takes care of the rest (i.e. spinning the motor).

I don't want to muck up Matt's tutorial string so I will post this as a seperate topic. Thanks for the info.

The throttle is now finished, ready to use! You merely supply 24 to 48 volts to the black and red input wires...

Matt, sorry for a newbie question, but many of the friction-drive RC builds are using 5S and 6S (18.5V / 22.2V). What changes would I have to make to this Magura throttle adaptation, or is a generic servo-tester really the best option for the lower-powered set-ups? (I don't even know if I'm asking the right question...)

The throttle is now finished, ready to use! You merely supply 24 to 48 volts to the black and red input wires...

Matt, sorry for a newbie question, but many of the friction-drive RC builds are using 5S and 6S (18.5V / 22.2V). What changes would I have to make to this Magura throttle adaptation, or is a generic servo-tester really the best option for the lower-powered set-ups? (I don't even know if I'm asking the right question...)

My current throttle I am building uses a very wide range input regulator. You can go as low as 6 volts input, if I remember correctly.

Matt

1% of the world's population can think "Outside the box". The rest are firmly stuck within the box. Where are you?

Just for info and to help anyone starting out .. I just tackled this ESC /servo tester throttle mod using the Turnigy servo tester .http://www.hobbycity.com/hobbyking/stor ... rvo_Tester PS.. initially i thought i had screwed up and got the wrong servo tester. ! but.... This actually proved simpler than the others, requiring only the insertion of one jumper (after removal of the pot) from the input "signal " pin ,to the centre pin of the potentiometer socket. So when used with an ESC /BEC , you can simply connect the throttle via the "input" socket of the (modified) servo tester and away you go ! Nice simple , quick , clean throttle interface. ! To recap..1) remove the potentiometer.2) insert a jumper lead from the input signal pin to the potentiometer socket centre pin location.3) reassemble and plug in your throttle.

And for Spinningmagnets.. this is used on an 18.5 V system, Turnigy Kforce 100A ESC, with the 63-54 motor, and a Hall effect thumb throttle.

Last edited by Hillhater on Thu Sep 16, 2010 8:44 pm, edited 2 times in total.